The present invention relates to an air conditioner for use in automobiles and, more particularly, to a blowout temperature control system to automatically control a temperature of a blowout air.
A conventional blowout temperature control system of an air conditioner for use in an automobile is disclosed in, for example, JP-A-62-2347l2. According to this system, for a change in opening position of an air mixing door as heat exchangeable means, a temperature sensor to detect a blowout temperature is attached at an outlet port in which a blowout temperature changes in correspondence to the opening position of the air mixing door. The opening position of the air mixing door is controlled such that the difference between a detection signal from the temperature sensor and an object blowout temperature signal which has previously been calculated approaches 0. That is, the air mixing door is controlled in a one-to-one corresponding relation between one air mixing door and one blowout temperature detecting sensor (hereinbelow, referred to as a duct sensor). According to this system, in response to a change in blowout mode (bilevel blowout, defroster blowout, or the like) of the air conditioner, the duct sensor corresponding to each air mixing door is also switched (for instance, the switching from the ventilation duct sensor to the defroster duct sensor is performed). However, at a certain time, one duct sensor certainly corresponds to one air mixing door and operates.
On the other hand, the function on the air conditioner unit side is disclosed in, e.g., Japanese Utility Model Laid open No. 62-3304. This cited reference proposes a system in which the blowing mode, i.e., a wind amount ratio from each outlet port is continuously changed to eliminate a sense of incompatibility when the blowing mode is switched.
The above conventional technique switches the corresponding duct sensor in response to a change in blowing mode and uses. In general, for a predetermined opening position of the air mixing door, the air temperature at each outlet port differs (the temperature at the ventilation outlet port is set to be low and the temperature at the floor outlet port is set to be high in order to obtain an ideal temperature condition such that the area around the head is cool and the area around the feet is warm). Thus, there occurs a problem such that when the duct sensor is switched, the signal becomes discontinuous and the blowout temperature suddenly changes. According to the conventional mode switching, when the duct sensor is switched, the outlet port also simultaneously changes by 100% (i.e., the outlet port is fully closed or opened). Therefore, the sudden change in the blowout temperature does not occur and since the outlet port itself changes, the passengers do not delicately feel the change in the blowout temperature.
To solve the foregoing problems, a method whereby the duct sensor to be used is fixedly set to either one of the duct sensors in place of switching the duct sensors is known. According to this method, when the ratio of the blowout wind amount from the relevant outlet port decreases due to a change in blowing mode, the response speed (sensitivity) of the duct sensor deteriorates, so that an unstable phenomenon of the control system such as a hunting of the blowout temperature or the like occurs.
On the other hand, as another method of solving the foregoing problems, there is also proposed a method whereby a discontinuous amount of the signal from the duct sensor which is generated when the duct sensor is switched is previously predicted and this discontinuous signal is corrected upon control. However, the deviation in temperature of the air from each outlet port largely changes due to various conditions (opening degree of air mixing door, blowout wind amount, operating state of a compressor, and the like), so that it is difficult to perfectly correct the discontinuous amount.